Plane-wave and wavepacket neutrino flavor oscillations in vacuum in conformal coupling models

Abstract

We investigate neutrino flavor oscillations in vacuum within a general conformal coupling model. We first examine the flavor oscillations within the plane-wave description of neutrinos, and then we extend our analysis to the wavepacket-based formalism. In both cases, we derive the general formulas for the flavor transition probability in arbitrary static and spherically symmetric spacetimes. We thoroughly discuss and assess in both cases the different possible ways -- dictated by the presence of the conformal coupling -- of computing the flavor transition probability. We show that the conformal invariance of the Dirac equation implies that the effect of conformal coupling on neutrino flavor oscillations modifies the oscillation length, but preserves the coherence length and unitarity. A detailed application to two-flavor neutrinos is then made and a numerical analysis is conducted within the well-known chameleon conformal coupling model.